Nasal cavity (nasal fossa)

Anatomy and subdivisions

The anterior part includes the vestibule, protected by hairs and stratified epithelium. Posteriorly the cavity contains three turbinates (conchae) — inferior, middle and superior — that project from the lateral wall and create the corresponding meatuses. The olfactory cleft occupies the superior region and contains olfactory epithelium. Openings from the frontal, maxillary, sphenoid and ethmoid sinuses and the nasolacrimal duct communicate with the nasal passages.

Tissues, blood supply and innervation

Most mucosa is respiratory epithelium (pseudostratified, ciliated columnar cells with goblet cells) supporting mucociliary clearance. The superior region contains olfactory receptor neurons that convey smell to the brain via the olfactory nerve (cranial nerve I). Arterial supply is rich, including branches from the sphenopalatine and ethmoidal systems; an anastomotic area on the septum (Kiesselbach's area) is a common site of anterior epistaxis. Sensation is supplied by branches of the trigeminal nerve (V1 and V2) while autonomic fibers regulate glandular secretion and vascular tone.

Functions

The nasal cavity filters, warms and humidifies inspired air, aiding lower airway health. Mucociliary transport removes particulates and microbes and directs mucus toward the nasopharynx. Olfaction provides the sense of smell and contributes to flavor perception. The nasal resonating chambers also influence voice quality. Proper drainage of the paranasal sinuses through the nasal passages is important for sinus ventilation and infection prevention.

Development, variation and clinical relevance

Embryologic fusion of facial prominences forms the nasal passages and choanae; congenital anomalies can include choanal atresia and nasal dysplasia. Common clinical problems include deviated septum, allergic and infectious rhinitis, sinusitis, nasal polyps, turbinate hypertrophy, epistaxis and anosmia. Traumatic or postsurgical defects may cause septal perforation or cerebrospinal fluid leak. Examination uses anterior rhinoscopy and nasal endoscopy; imaging (CT) evaluates sinuses. Treatments range from conservative measures (saline irrigation, topical steroids, antihistamines) to procedures such as septoplasty, turbinate reduction and endoscopic sinus surgery.